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Biomedical subjects

M A Harrison

Publications and source records attributed to M A Harrison.

At least 55 records · Page 3Linked to original sources
PubMed1989

Development of a three-channel, 24-h ambulatory esophageal pressure monitor.

We have developed a three-channel ambulatory esophageal pressure monitor and tested it with a series of 24-h studies. The monitor is a battery-operated, microprocessor-based device that measures pressures from three transducers positioned in the esophagus, stores the data in its memory, and transfers the data to an IBM PC computer system at the end of the recording period. Programs on the PC then analyze the data and identify contractile events, categorizing them according to specific parameters. Other programs display the pressure waveforms on the PC and allow visual inspection of the entire recordings or, alternatively, of particular events of interest. The system detects contractile abnormalities in patients with intermittent, noncardiac chest pains. We tested the system on ten normal subjects and found a relatively high incidence of what are usually considered "abnormal" contractions.

Esophagus↗
PubMed1988

The Geriatric Mental State (GMS) used in the community: replication studies of the computerized diagnosis AGECAT.

Three studies are reported using the Geriatric Mental State in one of its community forms on a total of 647 subjects aged over 65 and living in their own homes. The concordance between the computer diagnosis AGECAT and psychiatrists' diagnosis is at least as good in these replication samples as in the original studies (Copeland et al. 1986). AGECAT has been shown to be useful for epidemiological surveys and as a diagnostic guide for non-medical interviewers.

Diagnosis, Computer-Assisted↗
PubMed1987

Airborne aflatoxin in corn processing facilities in Georgia.

Problems affecting the health of agricultural workers in processing facilities where grains are contaminated with aflatoxin have been noted previously. Airborne particulates produced during processing are reported to produce various carcinomas when inhaled by factory workers. Two corn processing plants within Georgia were surveyed during the fall of 1984 and 1985 with utilization of an Andersen 6-stage air sampler, a high-volume air sampler and a slit sampler. No airborne aflatoxin was found; however, 10% of settled dust samples were contaminated with aflatoxin. The average particles were found to be globular in shape with an effective diameter between 2 to 3 microns. Only 30% of the bulk corn samples contained aflatoxin, which was present at low levels (0.15 to 8 ppb).

Aflatoxins↗
PubMed1986

Evaluation of particulate air samplers for airborne aflatoxin B1.

Five air samplers (Millipore, all-glass impinger, centrifugal, Andersen, and absorbent cotton) were evaluated for their ability to collect airborne grain particles contaminated with aflatoxin B1. Corn dust containing 100 micrograms aflatoxin B1/g was aerosolized within a containment system. Each device sampled 100 I air, thus exchanging the air in the chamber two times. Aflatoxin B1 was extracted from all sampling matrices and was detected and quantitated with thin-layer chromatography and scanning fluorodensitometry. The highest efficiency was obtained with the Millipore sampler, while the efficiencies of the centrifugal and the cotton samplers were almost identical. Efficiency of an Andersen was less, with no toxin recovered from an all-glass impinger. Measurement of particle size was accomplished with the Andersen sampler.

Aerosols↗
PubMed1986

Evaluation of ethylene as a mediator of gravitropism by tomato hypocotyls.

Assessments of the participation of ethylene in gravitropism by hypocotyls of tomato (Lycopersicon esculentum Mill.) indicate that gravitropism can occur without substantial change in ethylene production. Moreover, lowering or evaluating ethylene over a considerable range, as well as inhibiting ethylene action, fails to influence gravitropic bending. This vitiates the possibility that ethylene is a mediator of the primary, negative gravitropic response of tomato shoots.

Amino Acids↗
PubMed1985

Selective and differential medium for detecting Clostridium botulinum.

A selective and differential growth medium was developed for detection of Clostridium botulinum types A, B, and F. The medium consisted of peptone-glucose-yeast extract agar supplemented with cycloserine, 250 micrograms/ml; sulfamethoxazole, 76 micrograms/ml; and trimethoprim, 4 micrograms/ml as selective inhibitors and various types and levels of botulinal antibodies for type differentiation in the immunodiffusion reaction. Growth of proteolytic types of C. botulinum were not affected by the incorporation of the selective agents, but some nonproteolytic types were suppressed. Cross-reactions between types A and B were visually distinguishable, whereas cross-reactions between type F and Clostridium sporogenes did not occur at the optimum antibody titer. Optimum antibody titer varied with toxin type. The proposed selective differential medium should be valuable in isolating and typing of proteolytic C. botulinum types A, B, and F from samples containing mixed microbial populations.

Antitoxins↗
PubMed1984

The role of hormone transport and metabolism in apical dominance in oats.

14C-benzyladenine (BA) and 14C-indole-3-acetic acid (IAA) were used to study hormone transport to the tiller bud and hormone catabolism in excised oat stem segments. Acropetal BA transport was greatest from upright stem segments to tiller buds suppressed by apical dominance. IAA, abscisic acid (ABA), and C2H4 inhibited BA transport to the tiller bud. IAA transport to the tiller bud site was inhibited by BA, C2H4, or after gravistimulation, which affected BA transport to a lesser extent than IAA transport. Multiple peaks of radioactivity were observed in 14C-BA- or 14C-IAA-treated stem segments after 9 h of transport. IAA, ABA, and C2H4 promoted BA catabolism. Auxin, ABA, and C2H4 may inhibit tiller bud release by inhibiting cytokinin transport to the tiller bud and by promoting cytokinin catabolism. Gravistimulation may promote tiller release by inhibiting IAA transport to the tiller bud and allowing cytokinins to accumulate there preferentially.

Abscisic Acid↗
PubMed1983

Endogenous auxin and ethylene in pellia (bryophyta).

The occurrence of endogenous indole-3-acetic acid and ethylene in bryophyte tissue was tentatively demonstrated using gas chromatography, high performance liquid chromatography, and double-standard isotope dilution techniques. Rapidly elongating stalks (or setae) of Pellia epiphylla (L.) Corda sporophytes contain approximately 2.5 to 2.9 micrograms per gram fresh weight of putative free IAA. Ethylene released by setae increases during growth from 0.027 to 0.035 nanoliter per seta per hour. Application of 5 microliters per liter ethylene inhibits auxin-stimulated elongation growth of this tissue, a result which suggests that both endogenously produced compounds act in tandem as natural growth modulators.

Journal Article↗
PubMed1983

Control of alpha-mannosidosis in Angus cattle.

Tests for the detection of animals heterozygous for alpha-mannosidosis were undertaken on samples taken from 34,203 cattle registered with the Angus Society of Australia. Results indicates 1,836 (5.4%) of the animals were heterozygotes. Heterozygotes were detected in 214 (51%) of the herds examined.

Animals↗
PubMed1982

Does ethylene play a role in the release of lateral buds (tillers) from apical dominance in oats?

The growth of lateral buds (tillers), which are undergoing release from apical dominance, was measured in upright and gravistimulated intact Avena sativa L. cv. ;Victory' (oat) shoots as well as in isolated Avena stem segments treated with kinetin and sucrose. During release, the tiller bud initially shows a slow rate of elongation accompanied by swelling. It is followed by a more rapid rate of elongation. Ethylene (C(2)H(4)) production in shoot segments containing a tiller bud was found to occur at the onset of tiller swelling during gravistimulation as well as during inflorescence emergence. Exogenous application of indoleacetic acid or C(2)H(4) inhibits kinetin-induced tiller bud swelling and elongation. However, stem segments pulsed for 24 hours in C(2)H(4) or the C(2)H(4) biosynthesis precursor, 1-amino-cyclopropane-1-carboxylic acid (ACC) and then transferred to kinetin and sucrose, showed a significant increase in swelling elongation as compared with segments maintained under the same conditions but without C(2)H(4) or ACC in the pulse. Segments pulsed for 24 hours with kinetin and sucrose plus the ACC biosynthesis inhibitor, aminoethoxyvinylglycine, or the C(2)H(4) action inhibitor, CO(2), then transferred to kinetin and sucrose medium, showed inhibition of tiller swelling during the pulse and of subsequent elongation. These results indicate that C(2)H(4) plays a role in promoting tiller swelling during the onset of tiller release from apical dominance and may act as a modulator hormone in promoting tiller elongation in the presence of cytokinin.

Journal Article↗
PubMed1980

Hormonal Regulation of Lateral Bud (Tiller) Release in Oats (Avena sativa L.).

Stem segments containing a single node and quiescent lateral bud (tiller) were excised from the bases of oat shoots (cv. ;Victory') and used to study the effects of plant hormones on release of lateral buds and development of adventitious root primordia. Kinetin (10(-5) and 10(-6) molar) stimulates development of tillers and inhibits development of root primordia, whereas indoleacetic acid (IAA) (10(-5) and 10(-6) molar) causes the reverse effects. Abscisic acid strongly inhibits kinetin-induced tiller bud release and elon-gation and IAA-induced adventitious root development. IAA, in combination with kinetin, also inhibits kinetin-induced bud prophyll (outermost leaf of the axillary bud) elongation. The IAA oxidase cofactor p-coumaric acid stimulates lateral bud release; the auxin transport inhibitor 2,3,5-triiodo-benzoic acid and the antiauxin alpha (p-chlorophenoxy)-isobutyric acid inhibit IAA-induced adventitious root formation. Gibberellic acid is synergistic with kinetin in the elongation of the bud prophyll. In intact oat plants, tiller release is induced by shoot decapitation, geostimulation, or the emergence of the inflorescence. Results shown support the apical dominance theory, namely, that the cytokinin to auxin ratio plays a decisive role in determining whether tillers are released or adventitious roots develop. They also indicate that abscisic acid and possibly gibberellin may act as modulator hormones in this system.

Journal Article↗